Assessment of Heavy Metal Pollution in Surface Waters and Bioaccumulation in Fish: Implications for Human Health Risk‎

Abstract

Heavy metal pollution in surface waters, driven by rapid industrialization, urbanization, agricultural runoff, and geogenic weathering, poses a persistent global threat due to the metals’ non-biodegradable nature, high toxicity, and tendency to bioaccumulate and biomagnify through aquatic food chains. This comprehensive review examines the geochemical and anthropogenic sources of key metals (Hg, Pb, Cd, Cr, As, Ni, Cu, Zn), the physicochemical factors (pH, temperature, redox, salinity, seston) governing their speciation and bioavailability, and the mechanisms of uptake, tissue-specific distribution, and trophic transfer in fish. Fish serve as critical bioindicators, with highest accumulations typically observed in liver, kidney, and gills (via metallothionein sequestration), while muscle tissue often shows lower levels except for highly lipophilic methylmercury.

Standard metrics Bioconcentration Factor (BCF), Bioaccumulation Factor (BAF), Biomagnification Factor (BMF), and Trophic Magnification Factor (TMF) quantify exposure pathways, revealing pronounced biomagnification of mercury. Human health risk assessment frameworks, including Estimated Daily Intake (EDI), Target Hazard Quotient (THQ), Hazard Index (HI), and Carcinogenic Risk (CR), demonstrate that chronic consumption of contaminated fish can exceed safe thresholds, leading to neurotoxicity, nephrotoxicity, carcinogenicity, and developmental disorders. The review also evaluates conventional and emerging remediation strategies (chemical precipitation, bioremediation, biochar, and nanotechnology such as nZVI) and highlights regional vulnerabilities exacerbated by climate change. Findings underscore the urgent need for integrated monitoring, stricter emission controls, and sustainable remediation to protect aquatic ecosystems and safeguard public health.